[luckyharr]

I think the last well known pitcher to feature a screwball was Fernando. Put your right arm out with your palm up. Now rotate your thumb forwards as far as you can (should be able to go less than 360 dergrees.) Now imagine making that motion while throwing a ball at top speed. It is not good for your shoulder and probably not fun for your elbow either. The curveball motion, the exact opposite, seems more natural. It's also true that split fingers, circle changes, and some types of sinkers all have a similar pitch arc, are easier to learn, and are likely less taxing on the arm.